ESTIMATION OF RELATIVE ECONOMIC VALUE FOR HERD LIFE OF DAIRY-CATTLE FROM PROFILE EQUATIONS

Lifetime records of 122,679 cows from 7557 herds, obtained from Mid St ates Dairy Records Processing Center (Ames, IA), were used to determin e net income and net income for the planning horizon. With a planning horizon of five lactations for each cow, the estimated profit from the replacements was credited to each cow not surviving until fifth calvi ng. Net income was defined as lifetime income minus costs. Net income for the planning horizon was defined as net income plus profit from re placements within the planning horizon. Income was from the sale of mi lk, calves, and culled cows. Costs were included for heifer rearing, f eed, labor, and breeding. Longer herd life yielded greater profit for net income and net income for the planning horizon. The rate of increa se in profit for longer herd life was reduced for net income for the p lanning horizon, which accounts for profit from cows replacing a culle d cow compared with profit from net income. The relative economic valu e (phenotypic standard deviation basis) of production to herd life was 0.18:1 for net income and 0.46:1 for net income for the planning hori zon. The relative value for herd life was overestimated by about 2.5 t imes when profit from replacements was not considered. Values for prod uction relative to herd life increased for high milk prices and low fe ed prices. Lower prices for culled cows in combination with high price s for milk and feed increased the relative economic value of productio n.